What is a vibrating penis pump?

Short Answer:
A
vibrating penis pumpis a tube that creates a vacuum around the penis, causing it to
become engorged, that also contains a small vibrator for additional
stimulation.

Long Answer: Penis pumps
use a vacuum tube around the penis to force blood into the member,
thereby making it longer, harder, and bigger than it normally is in its
erect state. Some people claim that prolonged use of pumps can
permanently increase penile length by stretching the ligaments in the
penis. The efficacy of this technique has not been proven.

Nevertheless, penis pumps
do provide at least temporary
erection enhancement, and many men find
the suction provided by the pumps to be very stimulating, sort of like a
mega blow job. A vibrator in the pump can increase the level of
stimulation. Usually the vibrators in penis pumps are small bullet or
egg vibrators located at the base of the shaft, but some have vibrators
placed at the top of the tube. If you're pumping to achieve size and
length a vibrator in your penis pump isn't going to make any difference.
But if you're using it as a masturbation toy, a vibrator can turn your
pump job into a hummer.